This invention relates generally to deep fat fryers for cooking foods and particularly to deep fat fryers of the so-called "instant recovery" type.
It is well known that in cooking foods in deep fat fryers, the amount of fat absorbed by the food and the rate of heat absorption have marked effects on the taste, appearance and quality of the cooked food and on the useful life of the cooking fat. Prior to the development of the instant recovery deep fat fryer in the 1950's, it was customary to maintain a large volume of "working fat" at sufficiently high temperature to meet the peak demands of foods having the greatest heat requirements to avoid producing "greasy" fried foods caused by the existence of large temperature gradients in the fat during cooking.
The instant recovery fryer essentially eliminated the recovery time portion of the prior art cycle which was divided into pre-heat time, frying time and recovery time to bring the fat back to frying temperature. With the instant recovery fryer, the cooking fat was brought back to frying temperature at the end of the frying time.
The instant recovery deep fat fryer enabled an increase in the then standard 8.86.degree. F. per minute fat heat-up rate to as much as 56.degree. F. per minute, without damage to the fat, provided there was a proper minimization of non-working fat. The smaller amount of fat in the fryer yielded a great improvement in fat economy. Working the fat at a more uniform temperature and exposing less fat to the atmosphere also had the beneficial effect that the fat in these fryers experienced less contamination during normal cooking and thus had an extended working life.
In U.S. Pat. No. 4,041,852 issued Aug. 16, 1977 to Richard T. Keating, problems in minimizing the amount of working fat in a deep fat fryer are addressed. The solution propounded in the patent is to provide a plurality of removable fat displacers to minimize the volume of fat in the vessel for cooking food products having surface to volume ratios less than that normally characteristic of small cut French fries. The purpose was to dispense with the need for having to change fat because it becomes contaminated and unfit to produce quality foods. The instant recovery fryer, with fat displacers to minimize the amount of fat, resulted in the undesirable free fatty acids being kept within acceptable limits by the periodic addition of make-up fat to replace the fat absorbed during cooking.
The technique taught in the patent involved the insertion of appropriately contoured fat displacement elements of extruded aluminum in various positions around the heat transfer tubes in the heating section of the vessel and around the food baskets in the cooking section of the vessel. The fat displacers were removable because of the need to periodically clean the fryer to remove crumbs and food particles that may have settled on the upper surfaces of the heat transfer tubes and on the bottom of the vessel. This requirement imposed a substantial burden on the operator and the system has not found wide acceptance in the food service industry.
Accordingly there still exists a need in the art for a deep fat fryer capable of the high heat exchange necessary for cooking foods having large heat input requirements in vessels of minimum surface area and volume for maximizing the working life and quality of the cooking fat.